Reverse osmosis, as a procedure for the purification of liquids, particularly water, has gained favor in the last two or three decades. Unlike evaporation plants that have been used for the purification of seawater, reverse osmosis equipment does not require a source of heat energy. Rather, virtually any type of prime mover may be utilized to operate a pump capable of pressurizing the liquid to be purified to the requisite pressure. Consequently, reverse osmosis units, and the locations in which they are operated, are not limited by the presence or absence of heat energy.
In addition, reverse osmosis purification equipment is readily sized for particular applications simply by providing the requisite area of membrane and a pump of appropriate capacity. Because of these characteristics, reverse osmosis purification units are ideally suited for installation at remote sites to which they may be transported, without disassembly, and put into immediate operation.
One such unit is the ROWPU (Reverse Osmosis Water Purification Unit) developed in 1979. ROWPU units were trailer mounted and included a diesel driven electrical generator. The electrical generator is employed to operate six electrically operated pumps, including two raw water pumps, a backwash pump for a primary filter, a feedwater booster pump for providing feedwater at a relatively low pressure, a high pressure pump for elevating the pressure of the feedwater to a pressure whereat reverse osmosis can occur at an economically practical rate, and a product water pump. The ROWPU also had an automatic, timer operated, backwash system for the primary filter. A number of its components were made of fiberglass so as to avoid corrosion problems. However, the use of fiberglass construction gave rise to mechanical weakness and increased rates of mechanical failure. Furthermore, in operation, the unit was noisy due to the noise made by the diesel operated electrical generator, and the use of extensive electrical systems resulted in a unit having substantial complexity with a high rate of mean time between failures.
The present invention is directed to overcoming one or more of the above problems.